Elevation of granular solids



WNW

July 20, 1954 w. L. MOCLURE ELEVATION OF GRANULAR SOLIDS Filed June 19, 1951 INVENTOR. WILLIAM L. MC CLURE ATTOR N EYS Patented July 20, 1954 ELEVATION OF GRANULAR SOLIDS William L. McClure, Toledo, Ohio, assignor to Sun Oil Company, Philadelphia, Pa., a corporation of New Jersey Application June 19, 1951, Serial No. 232,282

2 Claims.

This invention relates to the. elevation of granular solids by means of a lifting gas, and more particularly to the separation of the solids from gas after such elevation.

It is known in the art to elevate granular solids from a lower zone to a higher zone by suspending the solids in a lifting gas under pressure in the lower zone and passing the lifting gas, having solids suspended therein, through a confined lift conduit to a higher zone. When the mixture of solids and gas reaches the higher zone the solids are generally separated from the gas by discharging the mixture from the lift conduit into an expansion space provided by a disengaging vessel above and communicating with the lift conduit outlet. As the solids and gas rise above the lift conduit outlet the gas expands and decreases in velocity and the solids correspondingly decrease in velocity and are enabled to reverse their direction of vertical movement and fall to the bottom of the disengaging vessel. Generally the solids are collected in the bottom of the disengaging vessel as a compact mass and can be removed therefrom for further use. The lifting gas can be removed from the disengaging vessel substantially separately from the bulk. of the granular solids. The lifting gas will generally contain fine solid particles entrained therein and these fine particles can be removed from the gas by passing the latter through a cyclone separator or other suitable separating means.

An important industrial application of a gas lift system as described above is in commercial processes for hydrocarbon conversion utilizing granular solid contact material. In the moving bed manner of conducting such processes it is known to gravitate granular solids as a compact mass through reaction zones to a low level in the system of apparatus and then suspend the solids in a lifting gas and elevate them to a high level in the system from which they are again gravitated through the reaction zones to provide a continuous circulation type of operation.

In gas lifting operations of the type described above and particularly in operations where rela tively coarse granular solids are elevated through elongated lift conduits, it is necessary to impart to the solids a high velocity in order that those solids may be continuously elevated through the elongated lift conduit. By elongated lift conduit it is intended to indicate a conduit for example whose vertical height is at least 50 times the major dimension of the lift conduit cross sec tion. Because of the high velocity which the solids must have as they issue from the lift conduit outlet those solids rise a substantial distance above the lift conduit outlet before they are enabled to reverse their direction of vertical movement and fall into the bottom of the disengager. With most granular solids which are handled in the manner considered herein, the attrition undergone by the solids upon falling through a substantial distance such as the distance from the top of their height of rise in the disengager to the level beneath the lift conduit outlet at which their fall is abruptly arrested, is relatively high. Since attrition of the solids is in most cases a highly undesirable effect resulting in high rates of loss of the solids from the system, it is desirable to avoid such attrition as much as possible.

According to the present invention, solids are elevated by means of a lifting gas through a confined elongated lift conduit and are discharged from the lift conduit outlet into a disengaging vessel and the solids are collected in the disengaging vessel in a manner providing less attrition than occurs when prior art methods of collecting the solids are employed. According to the present invention the solids and gas are passed upwardly into the disengager through a substantially vertical distance of rise and are then reversed in their direction of vertical movement and passed downwardly together in the disengager. The lifting gas while passing downwardly also moves laterally in the disengager into a collection zone which is laterally disposed with regard to the stream of gas and solids which is rising above the lift conduit outlet. The collection zone is positioned at a level above the lift conduit outlet so that the lifting gas after reversal of direction passes downwardly through a vertical distance of descent which is less than the distance of rise through which it moved before reversing direction. As the lifting gas moves downwardly and laterally through the disengaging vessel it laterally displaces the falling solids toward the collection zone. At least a portion of the solids thus displaced are intr0- duced into the collection zone together with the lifting gas. The remainder of the solids fall beneath the level of the lift conduit outlet in the manner which is usual in the operation of gas lift disengagers. The portion which passes into the collection zone has its fall arrested after a shorter distance of fall than the solids which pass to a level below the lift conduit outlet. Accordingly the former solids undergo less attrition than the latter and the overall average attrition is less than is obtained when all the solids fall into the bottom of the disengager. After introduction into the collection zone the lifting gas moves laterally therein and is then removed from the collection zone through a path which is initially upward in direction to provide an opportunity for the bulk of the solids which are introduced-into the collection zone to fall out of the lifting gas stream and be collected in the bottom of the collection zone. The solids are then removed from the collection zone in any suitable manner and can be commingled again with those solids which fell to the bottom of the disengager. The lifting gas after the removal from the collection zone can be passed as usual to separating means such as a cyclone separator in order that fine solid particles can be removed therefrom.

According to the present invention a plurality of collection zones can be used vertically spaced apart from one another. When this is done each collection zone receives a portion of the lifting gas and a portion of the granular solids which are displaced from the falling solids stream toward the collection zones. Solids can then be removed from each collection zone and commingled together with the solids which fall into the bottom of the disengager. The solids collected on the bottom plate of an upper collection zone can be commingled with solids collected in lower collection zones by passing solids downwardly through apertures in the bottom plate, or alternatively the commingling of solids can be effected exteriorly of the disengager, as subsequently described. Lifting gascan be removed from each collection zone and commingled for passage to separating means such as the cyclone separator. The advantage of using a plurality of collection zones over using a single collection zone resides in the fact that it is possible by the use of a plurality of collection zones to decrease the average distance of descent for the entire bulk of the solids which are handled in the operation. If only a single collection zone is used with its bottom situated at a relatively high level in the disengager a substantial proportion of the solids which issue from the lift conduit outlet will not rise sufficiently high in the disengager to be able to fall onto the bottom of the collection zone. If, on the other hand, the bottom of the collec-' tion zone is situated at a relatively low level in the disengager, the solids which rise relatively high in the disengager before reversing direction will have a relatively great distance to fall before striking the bottom of the collection zone. But if a plurality of collection zones are used the zones which are positioned relatively high in the disengager can receive after a short distance of descent those solids which rise relatively high in the disengager and the collection zones which are relatively low in the disengager can receive, after a short distance of descent, the solids which rise a relatively short distance in the disengager.

In order for the advantageous effects of the invention to be obtained it is necessary that a substantial portion of the lifting gas be reversed in direction after rising above the lift conduit outlet and pass downwardly and laterally with the falling solids so that the lateral component of the motionof the lifting gas can act to displace the solids laterally away from the rising stream toward the collection zones while the solids are falling in the disengager. This requires that the lifting gas outlet from the collection zone or zones be positioned at a level below the maximum this effect combined with the effect of the lifting gas which rises higher in the disengager and then passes downwardly to the lifting gas outlet in the collection zone, provides the advantageous re sults obtained according to the invention.

The invention will be further described with reference to the attached drawing. Figure 1 is a schematic diagram of a system of apparatus through which granular solids can be continuously circulated with elevation of the solids from a low level in the system to a high level therein. Figure 1 does not show any details according to the present invention, but merely illustrates a type of system to which the invention can be applied. Figures 2 and 3 illustrate details aocording to the present invention and are respectively a sectional elevational view and a sectional plan view of a disengaging vessel for use in a gas lifting operation.

Turning now to Figure 1 there are shown therein reaction vessels l0 and II, gas lift engaging vessel [2, lift conduit I3, and gas lift disengaging vessel l4. In operation granular solids are gravitated from disengaging vessel l4 through line l5 into reaction vessel Ill which may be for example a hydrocarbon conversion vessel. From vessel I 0 solids gravitate through line It into reaction vessel I I which may be for example a regenerator for contact material as used in the hydrocarbon conversion. From vessel ii the solids gravitate through line H into engager i2. Lifting gas under pressure is introduced into engager 12 through line l8 and granular solids suspended in that lifting gas and pass from engager I2 through lift conduit l3 into disengager l4. Granular solids are separated from the lifting gas and collected in the bottom of disenga H from which they are passed through line IE- to complete the cyclic operation. Lifting gas is removed from disengager l4 substantially sep arately from, the bulk of the granular solids through outlet means which are not shown in Figure 1 but are illustrated in Figure 2 subsequently described.

Turning now to Figures 2 and 3, there is shown therein disengaging vessel l4 above and communicating with the outlet 30 of lift conduit 53. Disengager l4 provides a cylindrical space directly above the outlet 30 of lift conduit i3, this space being bounded by the top 3! of disengager l4. Disengager It also provides an expansion space communicating with and laterally disposed relative to the space directly above the lift conduit outlet. This expansion space provides space in which lifting gas can expand toward side wall 32 of disengager M. The disengager M as illustrated in Figures 2 and 3 has a shape which is particularly well'adapted for use as one of a plurality of disengaging chambers each above and communicating with a lift conduit and all in communication with a lower solids collecting portion of the disengaging vessel. The use of such disengaging chambers is advantageous in some industrial applications as described in copending application Serial No. 203,323, filed December 5 29, 1950, by Clarence H. Thayer. It is to be understood that the invention is also applicable to a cylindrical disengaging chamber or vessel with which a single lift conduit is centrally positioned.

Within disengager l4 and secured to side wall 32 thereof are a plurality of vertically spaced apart transverse plates 34 each providing a bottom plate for a collection zone thereabove. Each plate 34 is downwardly inclined toward sidewall 32 of disengager l4. The inner surfaces 35 of the plates 34 are positioned outside the space directly above the top of lift conduit [3. Each bafiie 34 has an aperture 36 therethrough, as shown in Figure 3. These apertures 36 are so positioned that the aperture in none of the plates 34 is directly beneath the aperture of the plate directly above. Above each of the transverse plates 34 is a substantially vertical bafiie plate 3'! providing an inner wall for a lifting gas removal conduit 33. Secured to each baffle plate 31. is a horizontal top plate 39 which is also secured to side Wall 32 of disengager I. Also secured to sidewall 32 of disengager M are vertical baffles 40, shown in Figure 3, which provide sidewalls for the lifting gas removal conduits 38, which communicate with ports 4| in the disengager sidewall 32. Also communicating with ports 4| are external conduits 42 providing external extensions for lifting gas removal conduit 38.

The inner surface 35 of each plate 34 extends farther inwardly in disengager l4 than the inner surface 35 of the adjacent plate 34 thereabove. In this way the inner portions of the lower plates 34 are adapted to arrest the fall of solids which are not arrested by the higher plates 34.

In operation granular solids and lifting gas are discharged upwardly from outlet end 30 of lift conduit l3 into disengager l4. The solids and gas thus discharged pass upwardly as a rising stream through the space directly above the top of the lift conduit. As the ga rises it expands and decreases in velocity and the solids in the rising stream decrease in velocity and also move laterally to a small degree as they rise. When the solid particles decrease in upward velocity to zero, they fall back through the space between the rising stream of gas and solids and sidewall 32 of the disengager 14. A portion of the lifting gas discharged from lift conduit !3 passes upwardly and laterally into the collection zones between the transverse plates 34 and the remainder of the lifting gas passes upwardly to a relatively higher level, reverses indirection and moves downwardly and laterally into the collection zones. The lateral movement of both portions of lifting gas displaces the falling solids laterally toward the collection zones. Portions of the solids thus displaced enter the collection zones and are collected on the transverse plates 34. The remainder of the falling solids fall beneath the lowermost plate 34 and are collected in the bottom of disengager M. In each collection zone lifting gas passes laterally and then upwardly into the lifting gas removal conduits 38. As the gas moves upwardly in the conduits 38 most of the solid particles entrained by the gas fall backwardly onto the transverse plates 34. The lifting gas then passes through the ports 4| and the external conduits 42 and is conveyed to separating means such as a cyclone separator not shown. Solids are continually removed from each transverse plate 34 by gravitation through the apertures 36 onto the next lower plate 34. From the lowermost plate 34 the solids gravitate through the aperture 36 therein and fall into the bottom of the disengager M.

The operation above described is effective to reduce the attrition of the granular solids below the attrition which occurs when operation according to the prior art is carried out. By collecting the solids on the transverse plates 34 the distance, through which the solids fall from the top of their height of rise until having their fall abruptly arrested, is decreased. It has been found that the attrition of solid is less when they fall from the top of their height of rise to the bottom of the disengager in a series of stages, falling a short distance in each stage and having their fall arrested before falling into the next stage when the solids fall through the entire distance from the top of their height of rise to the bottom of the disengager without having their fall arrested at an intermediate level.

Removal of the lifting gas through the conduits 38 above the transverse plates 34 makes it possible to collect a greater proportion of the solids on the plates 34 than when the lifting gas is removed from the top of the disengager or when the lifting gas is all passed downwardly to the bottom of the disengager and removed therefrom. Removal of lifting gas in the manner contemplated in the present invention is further advantageous over removal of lifting gas from the top of the disengager, in that removal according to the invention requires that a substantial proportion of the lifting gas must reverse its direction of vertical movement and pass downwardly in the disengager with the result that the downwardly moving gas opposes in some degree the upward movement of solids and causes the solids to rise less high in the disengager than they otherwise would. Removal of lifting gas according to the invention is further advantageous over removal of lifting gas from the bottom of the disengager in that when the latter is done the lifting gas as it passes downwardly past the inner surface 35 of the lowermost plate 34, is traveling at high velocity since the area through which it must pass is relatively small at this level in the disengager. The high velocity of the lifting gas impart a high velocity to the falling solids and causes a relatively high degree of attrition in those solids which fall past the inner surface 35 of the lowermost plate 34 into the bottom of the disengager. For the reasons given above, it is generally preferred that substantially all gas be removed from the disengager at a level above the lowermost plate 34.

It is to be understood that according to the present invention means other than the apertures 36 can be used to remove solids from above the plates 34. For example the solids can be removed through apertures in the disengager sidewall 32 and through solids conduits communicating with such apertures. The solids thus removed can then be commingled with each other and with the solids removed through line [5, the commingling taking place exteriorly of disengager l4.

Also, although the plates 34, as illustrated in Figure 2, are secured to the disengager sidewall 32, it is to be understood that these plates can instead be supported with their lower ends horizontally spaced apart from the sidewall 32. In this case the solids collected on the plates 34 move laterally on. those plates and fall downwardly into the bottom of the disengager through the space between the lower portions of the plates 34 and the sidewall 32. .The principal function of the plates 34 as contemplated by the present invention is to temporarily arrest the fall of granular solids and the plates can therefore have any suitable construction adapted to serve this purpose. It is not strictly necessary that the plates 34 should be inclined toward the sidewall 32; however, such inclination is preferred in that it facilitates the removal of solids from above the plates.

The lifting gas removal conduits 38 can have any suitable construction. The inner walls 31 of those conduits can be positioned as shown in Figures 2 and 3, or they can be positioned any distance from the sidewall 32 provided that they are near enough to the sidewall 32 in order that the lifting gas must follow a lateral path for a substantial distance after entering the collection Zone above each plate 34 and before moving upwardly in the lifting gas removal conduits 38, and provided that there is sufficient space between the bafile 31 and the sidewall 32 for satisfactory removal of lifting gas. The present invention contemplates the use, for ex ample, of a pipe having a circular cross section instead of the walls 31, 39, and it which constitute the conduits 38 as shown in Figure 2. A suitable arrangement of this type can comprise, for example, an internal extension of the conduit :22 horizontally into the disengager and a vertical extension of the conduit downwardly from such internal extension. An inclined gas removal conduit can also be used, the one requirement being that it should have a substantial vertical component in order to provide a space through which lifting gas passes upwardly.

According to the present invention the vertical distance of the lifting gas removal conduit inlet above the transverse bafile is sufficiently great to provide a space through which gas may pass above the bafiie into the inlet without causing excessive turbulence or such high gas velocities that excessive amounts of solids are entrained and carried out of the collection zone through the lifting gas removal conduit. Also, preferably, the operating conditions employed are such that if solids are collected as a compact bed above the transverse baflle, solids are removed from the bed rapidly enough so that the top of the compact bed is beneath the lifting gas re moval conduit inlet. For a given solids elevation rate, a person skilled in the art can, in the light of the present specification, determine the proper positioning of lifting gas removal conduit inlets and the proper operating conditions to meet the above preferred specifications.

Although in Figures 2 and 3 the horizontal cross section of the disengaging chamber illustrated has the shape of a parallelogram and the lift conduit has its upper end positioned adjacent to the shorter base of the parallelogram, it is to be understood that the disengager can have any other suitable cross section, for example, a cylindrical disengager can be used, the lift conduit being positioned centrally with regard to the circular cross section of the disengager. In this case the transverse plates adapted to arrest the fall of granular solids preferably extend entirely around the space directly above the top of the lift conduit and either a plurality of lifting gas removal conduits spaced around the periphery of the disengaging vessel are employed, or an annular lifting gas removal conduit extending around the entire periphery of the disengager is employed.

The present invention is applicable to the elevation of granular solids generally and particularly to the elevation of mixtures of granular solids a major proportion of which are coarse granular solids which are large enough to be retained on a 20 mesh U. S. sieve series screen. When such mixtures are elevated by means of a lifting gas through an elongated lift conduit, it is necessary to impart a relatively high velocity to the solids and the momentum of the solids as they enter the disengager is therefore relatively large so that the height of rise of the solids in the disengager is relatively great and the attrition undergone by the solids is correspondingly great unless measures such as are taken according to the present invention are employed in order to reduce the attrition. The solids which are elevated can be of any suitable composition, for example, they may be catalytic materials such as are commonly used in the conversion of hydrocarbon materials, for example, natural or synthetic silica-alumina catalysts, or they may be inert heat transfer materials such as are also used to promote hydrocarbon conversion reactions. Other types of granular solids can be elevated and separated from lifting gas according to the present invention.

Any suitable lifting gas can be employed. The lifting gas can be inert relative to the solids which are elevated. Examples of this type of lifting gas are steam, air, and flue gas as used to elevate hydrocarbon conversion supporting contact material. The lifting gas can also be capable of undergoing a chemical reaction upon contact with the solids which are elevated. An example of this type of lifting gas is hydrocarbon vapor as used in the elevation, at a conversion. supporting temperature, of hydrocarbon conversion supporting contact material.

The present invention relates to the elevation of granular solids through elongated lift conduits, that is lift conduits whose vertical height for example, within the approximate range 50 to 300 times the major dimension of the lift conduit cross section. Such elongated lift conduits are commonly employed in commercial processes, particularly in hydrocarbon conversion processes as previously described wherein granular solids are elevated, for example, through distances of 250 feet or more, the lift conduits having diam-- eters, for example, of /2 to 2 feet. The solids velocity through lift conduits as employed in such processes is frequently such that the solids are traveling at a rate of 25 to 50 feet per second as they move upwardly past the outlet of the lift conduit into the disengager. It is generally preferred that the solids velocity should not be less than 15 feet per second when discharged from the outlet end of the elongated lift conduit; otherwise, some tendency to stall the lifting operation might be encountered. Solids velocities as contemplated here, can be calculated by using the following formula:

Where Us is the solids velocity in feet per second, Ug is the lifting gas velocity calculated by dividing the lifting gas volume rate in cubic feet per second by the average cross section of the lift conduit in square feet, D5 is the average particle diameter of the solids in feet, and

is the ratio of densities of the solids and the lifting gas.

The invention claimed is:

1. In apparatus for elevating granular solids by means of a lifting gas through a lift conduit and upwardly into a disengaging vessel providing therein a, space directly above the top of the lift conduit and providing, communicating with at least a portion of the periphery of said space, an expansion space for lateral expansion of lifting gas, the improvement which comprises: a transverse bafile adapted to arrest the fall of granular solids and positioned within said expansion space and above said top of the lift conduit and outside and below the top of said space directly above the top of the lift conduit; a lifting gas removal conduit having its inlet spaced above said baffle and below the top of said space directly above the top of the lift conduit, and having an entry portion upwardly extending from said inlet, said gas removal conduit communicatin with a port in the disengager wall; and means for removing solids from above said baflie.

2. In apparatus for elevating granular solids by means of a lifting gas through a lift conduit and upwardly into a disengaging vessel providing therein a space directly above the top of the lift conduit and providing, communicating with at least a portion of the periphery of said space, an expansion space for lateral expansion of lifting gas, the improvement which comprises: a plurality of transverse baflles vertically spaced apart from each other, each adapted to arrest the fall of granular solids and positioned within said expansion space and above said top of the lift conduit and below the top of and outside said space directly above the top of the lift conduit; a plurality of lifting gas removal conduits, one above each said bafiie, each lifting gas removal conduit having its inlet spaced above said bafile and below the top of said space directly above the top of the lift conduit, and having an entry portion upwardly extending from said inlet, said gas removal conduits each communicating with one of a plurality of ports in the disengager wall; and means for removing solids from above each baffle.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 688,693 Richter Dec. 10, 1901 2,246,349 Crum June 17, 1941 2,509,984 Marrow May 30, 1950 2,628,188 Kirkbride Feb. 10, 1953 FOREIGN PATENTS Number Country Date 278,858 Germany July 18, 1913 313,613 Germany Aug. 24, 1916 311,639 Great Britain May 16, 1929 

